Octane rating when mixing Regular gas (93octane) with Racing fuel (110) octane.

[not so famous bob]

Was talking with a friend on this, he says the Regular Gas (93 Octane) will Degrade the Racing gas (110 octane). I always thought it was the opposite. If you have and 20 gallon fuel tank and have 10 gallons of Regular 93 Octane gas and add 10 gallons of Racing Fuel at 110 Octane; what would be the Octane rating of the mixed fuel in the 20 gallon tank ? I'd say it would be somewhere around 101 octane. What say you on this ? I know you could run all 20 gallons of Racing fuel but at $12.00 per gallon that would be a $240.00 fill-up, can't afford this. Also, the 10% Ethanol in the 93 octane gas comes into the picture.... Also, what about mixing with Aviation gasoline.... I've heard good and bad on this, something like AvGas has additives to keep airplane carbs from icing up in higher altitudes. Any views on this ? This mixed gas is for my 69 Charger with a 383 Magnum engine, stock rebuild.
Tks
Bob32268

equal parts =1/2 of the total....

 

[AR67GTX]

I wonder if octane is even figured the same way for racing fuel as it is for commercial fuel. Makes a huge difference. A commercial 93 octane fuel today is equivalent to about 98 octane back in the 60s. Just wondering.

(R+M)/2

I run a 427 Corvette with 12:1 pistons (real 11.7 compression), 256/266 cam, and aluminum heads on 90 octane non-ethanol. I keep it timed at 18 degrees initial and 34 total and it runs great.

 

[MWbirdLOVER70]

Was talking with a friend on this, he says the Regular Gas (93 Octane) will Degrade the Racing gas (110 octane). I always thought it was the opposite. If you have and 20 gallon fuel tank and have 10 gallons of Regular 93 Octane gas and add 10 gallons of Racing Fuel at 110 Octane; what would be the Octane rating of the mixed fuel in the 20 gallon tank ? I'd say it would be somewhere around 101 octane. What say you on this ? I know you could run all 20 gallons of Racing fuel but at $12.00 per gallon that would be a $240.00 fill-up, can't afford this. Also, the 10% Ethanol in the 93 octane gas comes into the picture.... Also, what about mixing with Aviation gasoline.... I've heard good and bad on this, something like AvGas has additives to keep airplane carbs from icing up in higher altitudes. Any views on this ? This mixed gas is for my 69 Charger with a 383 Magnum engine, stock rebuild.
Tks
Bob32268

Why not go to Google and use an octane conversation chart by say Sunoco?

 

[WileE]

Enough already. I think it's time to bring in a REAL expert

 

[bob32268]

I wonder if octane is even figured the same way for racing fuel as it is for commercial fuel. Makes a huge difference. A commercial 93 octane fuel today is equivalent to about 98 octane back in the 60s. Just wondering.

(R+M)/2

I run a 427 Corvette with 12:1 pistons (real 11.7 compression), 256/266 cam, and aluminum heads on 90 octane non-ethanol. I keep it timed at 18 degrees initial and 34 total and it runs great.

If 93 Octane today is the equivalent to 98 Octane gas in the 60's, what was the Hi-test Octane rating we used to use in the 60's? I think I read somewhere that is was around 106 Octane ?
Tks,
Bob32268

 

[bob32268]

What's your piston height
906 head I assume
What's your cranking cyl pressure.

Definitely 906 heads....not sure of the other specs as the engine was rebuilt by a previous owner.
Tks,
Bob

 

[mrhemi]

Not sure I want to get involved in this fray, but the OP did not specify whether the racing fuel was leaded or not.
Back in the day, when I actually worked for Suncor (Canadian Sunoco), we did all of the different blends with pump unleaded, av gas and race gas. All were verified in the Waukeshaw knock engines in the lab. If the race fuel in question is unleaded, the straight ratio math formula can be used. If it is leaded race fuel, it is not that simple.

 

[hofferwood]

The lead makes it------------weigh more.

 

[Backrd.Junkyard]

Stock 383 rebuild. You should be able to run 93 Octane non ethanol pump without problems. If you do need to raise octane, buy a bottle of VP Octanium.

 

[cosgig]

Real world answer here…. I use a 50/50 mix of 90 octane ethanol free “rec” fuel and 110 leaded gas in my 6bbl Roadrunner. I can tell you that it runs much better when the 110 is used, when I used to have to go to the next town over to get the 110, and I was low on fuel, I would put the 90 in up at the corner first, then drive over to Brighton to get 110. It would run like crap until I put in the 110. Now that the station right at the corner sells both, I don’t have that problem. No science, no math, just real world results. And bonus, it smells good too!

 

[j-c-c-62]

Not sure I want to get involved in this fray, but the OP did not specify whether the racing fuel was leaded or not.
Back in the day, when I actually worked for Suncor (Canadian Sunoco), we did all of the different blends with pump unleaded, av gas and race gas. All were verified in the Waukeshaw knock engines in the lab. If the race fuel in question is unleaded, the straight ratio math formula can be used. If it is leaded race fuel, it is not that simple.

1. I'd treasure learning why tetraethyl lead complicates matters in this context
2. Additionally, to also learn how octane back in the day with blended at the pump Sunoco leaded gas then was analog calculated/proportioned for each fuel delivery

 

[j-c-c-62]

Enough already. I think it's time to bring in a REAL expert View attachment 1822038

He omitted COVID risk from assessment, so that was pre 2020?

Funny show/characters/plot.

 

[69conv]

The lead makes it------------weigh more.

Does it weigh more than a duck?

 

[j-c-c-62]

The lead makes it------------weigh more.

That touches on a related important point, and why over octaning (is that a word?) a motor can result in less potential power output.
Every additive in gasoline displaces an amount of gasoline, and unless the additive has more or equal BTU energy of gasoline, the remaining gallon of gasoline will have less total BTU per gallon, its slight but still a factor. Ethanol is a good relatable example here.

 

[mrhemi]

1. I'd treasure learning why tetraethyl lead complicates matters in this context
2. Additionally, to also learn how octane back in the day with blended at the pump Sunoco leaded gas then was analog calculated/proportioned for each fuel delivery

The addition of TEL to the fuel is not a linear, consistent octane increase. It depends on the constituent makeup of the base fuel. This means the only way to confirm octane numbers is with a knock engine.
All this means is that you cannot do a straight ratio calculation as you can by blended two unleaded fuels.

 

[RemCharger]

1. I'd treasure learning why tetraethyl lead complicates matters in this context
2. Additionally, to also learn how octane back in the day with blended at the pump Sunoco leaded gas then was analog calculated/proportioned for each fuel delivery

Don't treasure, grab a degree and report back!
Maybe this **** is so simple we can make our own!

 

[Photon440]

1. I'd treasure learning why tetraethyl lead complicates matters in this context

It's been well known that adding lead increases octane. It was a popular trick in the 1970s, with published tests showing the improvements, to mix unleaded and leaded gas. A 50/50 mix of regular leaded and regular unleaded resulted in higher octane than either on their own, due to the 'kick' of the lead being added to the unleaded. It was not logarithmic; the unleaded gained more octane than the leaded would lose from dilution.

By the time leaded gas was phased out (1990 in Canada) the actual amount of tetraethyl lead in leaded fuel had already been reduced so much that the boost was no longer of much effect.

 

[hofferwood]

Does it weigh more than a duck?

I checked with my psychic (sy-kick), and she said "Depends on the SIZE of the duck".

 

[AR67GTX]

If 93 Octane today is the equivalent to 98 Octane gas in the 60's, what was the Hi-test Octane rating we used to use in the 60's? I think I read somewhere that is was around 106 Octane ?
Tks,
Bob32268

The recommended octane rating for the 67 Corvette L88 was 103 the equivalent of Sunoco 260. I believe Sunoco 280 was rated 110 octane in the 60s.

 

[Jerry Hall]

All this discussion (crap), is worthless to me. I'm just doing what works for my cars. You have beat this horse to death.